Influence of Steel Surface Conditions On the Nitrogen Uptake During Gaseous Nitriding Process

Nitriding potential (Kn) is typically used as the main process parameter in automatic gas nitriding systems. The Kn value accounts to some extent for the catalytic properties of treated parts, however the influence of steel surface quality on nitriding results is not only limited to Kn variations.

In this present work, we examine the kinetics of nitrogen uptake for different types of steel with different types of surface finishing using thin foil nitriding experiments. The aim is to understand the correlation between the cumulative effect of atmosphere activity, ammonia dissociation on the surface, and nitrogen absorption, to the steel’s initial surface condition. Furthermore, the temperature dependence of the process between 450-580ºC (842-1076ºF) is investigated. Results of nitrogen diffusion simulations based on obtained nitrogen absorption functions are also presented.

Keywords: Gaseous Nitriding, Ammonia decomposition, Process simulation, Iron catalyst.